Prostheses (or prosthetics) are artificial devices that replace body parts (e.g., fingers, hands, arms, legs). Generally, prostheses may be used to replace body parts lost by injury or missing from birth. Existing above knee prostheses use a significant amount of energy to walk and run as compared to the energy that able bodied individuals use. This is due to the fact that existing above knee prostheses have significant energy loss while being used by a patient.